I'm a Fellow at the Adam Smith Institute in London, a writer here and there on this and that and strangely, one of the global experts on the metal scandium, one of the rare earths. An odd thing to be but someone does have to be such and in this flavour of our universe I am. I have written for The Times, Daily Telegraph, Express, Independent, City AM, Wall Street Journal, Philadelphia Inquirer and online for the ASI, IEA, Social Affairs Unit, Spectator, The Guardian, The Register and Techcentralstation. I've also ghosted pieces for several UK politicians in many of the UK papers, including the Daily Sport.

Is This The Final Technical Piece We Need For The Space Elevator?

The great problem in exploiting space is in getting up out of the Earth’s gravity well. As the man once pointed out, when you’re in orbit you’re not halfway to the Moon, you’re halfway to anywhere.

And our technologies of how to get out of that gravity well are really rather primitive. Being primitive makes them inefficient. Sure, Space X and the like are making them better. But we’re still basically lighting a vast amount of feul to get an aluminium tube up there. It’s just never going to be true that using this rocket technology we’ll end up with space being a cheap and everyday sort of thing. It’s just not possible, within the confines of rocketry, to make it cheap enough for that.

There’s also a marked lack of any even plausible theory as to how anti-gravity might exist. So we’re rather on the lookout for something else. And it’s been pointed out for decades that that something else could be a space elevator. Essentially, deliver an asteroid into Earth orbit and drop a wire down from it. Fox the wire to the ground and then you can climb the wire as an elevator does inside a building. Once done this is cheap and efficient and it brings the costs of getting into space right down. Excellent.

However, the problem has always been that we just don’t have the material to make that wire. Nothing at all that is strong enough to not break simply under its own weight. It has been thought for some time that carbon nanotubes might be able to do it. But no one knew how to make wire out of them. Until now:

An international team of scientists has successfully found a way to spin tens of millions of carbon nanotubes into a flexible conductive thread that’s a quarter of the thickness of human hair.

“We finally have a nanotube fiber with properties that don’t exist in any other material,” said lead researcher Matteo Pasquali of Rice University. “It looks like black cotton thread but behaves like both metal wires and strong carbon fibers.”

The thread has ten times the tensile strength of steel and is as conductive as copper, but is flexible enough to be wound around a spool or woven.

If you can wind it or weave it then you can certainly spin it into a cable. And that really might just be the last piece of the puzzle we need to build that desired space elevator.

It would certainly be an engineering challenge to build, this is true. But there’s, assuming this cable is indeed strong enough, no theoretical reason why it couldn’t be built, nor financial. And building one would indeed open up at the very least the inner solar system to us. For it really is true that the major cost and difficulty of doing so is getting the first 50 miles off the planet. If you can do that cheaply then there’s a vast opportunity out there.

OK, maybe this doesn’t excite you like it does me: I’d say that if this is so you obviously didn’t read enough science fiction as a teenager. Or perhaps I read too much, either way.

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The asteroid would have to be in geostationary orbit. It would have to have some sort of engines to manoeuvre it and keep it in stable orbit, so how will that be done?

Once connected to the ground, it’s speed of rotation will have to be sufficient to provide a force pulling it away from the Earth, equal to the force pulling it towards the Earth otherwise its orbit will decay or it will escape Earth’s orbit.

How will this be done?

Won’t the additional weight of an object cause an imbalance as it moves up from the Earth’s surface and towards the asteroid (and vice versa) thus continually altering the energy needed to maintain the force of escape and attraction in equilibrium.

So long as the counterweight is above geostationary orbit, centrifugal force will keep it directly above the base station located on earth – no addition force will be required. Yes the weight of an object moving up and down the “elevator” and the Coriolis effect will alter the the counterweight’s momentum. But so long as these effects are maintain to a degree were they do not cause orbital decay, centrifugal force will always pull the line taut and in an upward direction. Imagine a sling shot using the earths rotation as its momentum.

At the moment it doesn’t appear to be very strong though. If it were anywhere near the tensile strength needed for a space elevator, they’d be telling you. Currently they are not even saying it’s any better than other braided cord material on the market.

The relevant strength measure is gigapascals (GPa) I believe. What’s the GPa strength of this material. I believe that for a space elevator, we need a material that has 50GPa. Really high tensile strength steel might be 1.2 GPa. Something ten times that wouldn’t be enough but it is a really big jump in the right direction.

The best GPa material ever tested has topped out at 63GPa but that was a very small carbon nanotube. Scaling that sort of material up to the macro scale is still a work in progress.

It stands to reason that; if a single carbon nano tube attains greater than the required GPa; woven threads of the same material bundled into cable will at the very least approach the required strength. Does this reasoning hold up when used on materials we have data for, such as bundles of steal cable vs and individual cable?

There are a lot of technical errors here. First, nanotubes are overhyped. A nanotube cable is not limited by the strength of the nanotubes but the glue that holds the nanotubes together.

Second, rockets are not “inefficient.” They are among the most efficient engines known to mankind. Virtually all of the chemical energy in rocket propellant gets converted to kinetic energy.

The biggest problem with space elevators is economic. Elevator proponents seek to replace “inefficient” rockets that use “vast amounts of fuel.” But that “vast amount of fuel” accounts for less than 1% of launch costs. Rocket propellant costs pennies per pound. More important cost factors are labor/maintenance and (most importantly) capital costs, which for expendable rockets are amortized over a single flight.

The space elevator would reduce that 1% propellent cost, but requires a huge increase in the already-much-larger capital costs. That makes no sense. On top of that, the throughput of the system is terrible, because it takes almost two weeks to make a roundtrip. So, even if you could build one, it would not be cheap. Space-elevator advocates make it sound cheap by talking about recurring costs, ignoring the initial capital investment and the cost of money.

Regarding the statement, “It’s just never going to be true that using this rocket technology we’ll end up with space being a cheap and everyday sort of thing” — saying so doesn’t make it true. The late Maxwell Hunter, father of the Delta rocket, used to say that anyone who believes that either doesn’t understand the rocket equation or doesn’t know how much rocket propellant costs.

Yes nanotube cable strength may be limited by the bonds holding the nanotubes together (let’s not use the derogatory term glue), but that does not mean it is significantly weaker. The electronic bonds and/or mechanical connections may be nearly as strong as the tubes themselves. Ropes are a perfect example. In natural fiber, it’s the mechanical connections among fibers, in synthetic ropes it’s among molecules. I have no idea how true that will be for nanotubes, no human does, but we should look at it.

The term “inefficient” in reference to chemical rockets is a system term, not a narrowly defined term applying only to propulsion. A Delta IV Heavy rocket weighs about 1,600,000 pounds at launch to get 20,000 pounds of payload to escape orbit. So about 1.3% of takeoff weight is stuff we’re interested in, the other 1,580,000 pounds is used once and gone. Chemical rockets do not scale up well, so that is not likely to improve much. That is a well-known limitation of that system.

As for system throughput, how long does it take to prepare and launch a single use rocket, including closing activities to wrap up the mission? Weeks at least, sometimes months. We’ve had 50 years of practice with rockets, so that is not likely to improve much.

The HUGE unimaginable capitol costs and NRE for a space elevator would be amortized over years, hopefully decades. With the energy input being the primary recurring cost. Longer transit times are a bonus here. Instead of needing to store vast amounts of energy that is expended in a few seconds, we have multiple options to generate and input energy into the system at a much lower maintainable rate over the course of days.

The strength required for a cable material strong enough to support a orbital tensile structure would require a material that has a breaking length (the maximum length of a vertical column, at see level, that a material can suspend when supported only at the top.) of 4,960 kilometers at sea level.

However, The breaking length of a cable material is shortest at sea level then higher up on the cable and infinite at GEO. So when selecting a cable material it doesn’t have to have a Breaking length of 35,786 km.

Why? While the material would require a cable that carries it’s own weight up to a geostationary orbit ~36 kilometers above sea level, the loss of gravity and increase in centrifugal force the higher one travels up the apparatuses will decrees apparent gravity of said cable the higher you go.

Carbon nano tubes have a breaking length of about 4,700 at sea level – just under the specific strength required to engineer an orbital tensile structure. However Colossal Carbon tubes offer a solution with a 7000km breaking length. My understanding is that when using GPa to measure the strength needed for a cable material is that GPa just measures strength – disregarding the density or weight of the material.

I think the information provided in this article is very exciting! While we have made tremendous technical progress over the past 20 years – we’ve been stuck on this rock for far to long. I mean the last time we went to the moon, cell phones hadn’t been invented yet and calculators were the size of textbooks!